This invention relates generally to systems for filtering and distributing fluids to the subterranean soil environment. More particularly, this invention relates to a system capable of filtering and distributing fluid leachate from a septic tank or the like to the subterranean subsoil environment.
Subterranean fluid leachate carrying systems are known in the prior art. In the system described in U.S. Pat. No. 4,880,333, a plurality of parallel core sheets of identical geometry are wrapped with a leachate permeable geotextile fabric so as to provide a continuous, horizontally extending in-drain for placement in an excavation. The system is preferably buried in a layer of sand or other fill. Leachate can be fed from a septic system or tank through a wide fluid conduit provided over the in-drain. The wide fluid conduit distributes the leachate over substantially the entirety of the top of the in-drain for subsequent distribution along the core sheets to the subsoil environment. It has been asserted that when identical parallel core sheets of the type used in U.S. Pat. No. 4,880,333 are stacked together with only a geotextile fabric as separation between them, during back filling and/or handling of the system the initially separated core sheets with the wrapped geotextile fabric may be compressed, one core sheet nesting into the other. This nesting leads to areas of the overall system, which are less efficient at filtration and distribution of leachate to the subsoil environment. Additionally, as the geotextile fabric permeability may lessen due to, for example, biological growth, the leachate level around the adjacent core sheet rises. However, the system of U.S. Pat. No. 4,880,333 does not provide a mechanism to redistribute the leachate accumulation from one core sheet to another core sheet, decreasing the long-term efficiency of the system.
The system described in U.S. Pat. No. 6,048,131 discloses a plurality of parallel, alternating core sheets and spacers of specified dimension, wrapped in an over and under serpentine fashion with a leachate permeable geotextile fabric so as to provide a continuous, horizontally extending in-drain for placement in an excavation. The spacers comprise inert material such as perlite sandwiched between spacer sheets of different pitch diameter than the core sheets. The system is preferably buried in a layer of sand or other fill so that leachate can be fed from a septic system or tank through a fluid conduit overlying the in-drain for purposes of distributing the leachate downwardly through the in-drain to the subsoil environment. The disclosure of U.S. Pat. No. 6,048,131 asserts that use of alternating sizes of core sheets and spacers lessens the tendency of the core sheets to nest. This reference also briefly mentions the use of perforated core sheets and states that the perforations bleed leachate through the fabric into the adjacent spacer. This system does not provide a mechanism for leachate movement to non-adjacent core sheets or spacers. Thus, an optimum mechanism to redistribute leachate accumulation from one core sheet to another core sheet is not provided.
An object of the invention is to provide an improved system for filtration and distribution of fluid into the subsoil environment.
Another object of the invention is to provide a leachate filtration and distribution system that can efficiently transfer leachate accumulating in one part of the system to other parts of the system.
A further object of the invention is to provide an improved leachate filtration and distribution system comprising core sheets and geotextile fabric with increased subsurface contact area.
Briefly stated, one aspect of the present invention is an assembly comprising a plurality of parallel, alternating core sheets and spacers and at least one transfer sheet adjacent an edge of at least some of the plurality of core sheets. The spacers can be in sheet form.
The core sheets and spacer sheets of the present invention are separated by a leachate permeable geotextile fabric. The geotextile fabric may be wrapped in an over and under serpentine fashion to leave the tops of the core sheets uncovered, but the tops of the spacer sheets covered. Alternatively, the fabric may be disposed between selected core sheets and spacer sheets in other patterns to leave any of the tops or bottoms of any of the core sheets and/or spacer sheets uncovered.
The transfer sheet of the present invention functions to transfer fluid from a supply pipe to the adjacent edges of a plurality of core sheets, for subsequent distribution along a core sheet and through the geotextile fabric into the subsoil environment. Additionally, any fluid accumulating in the area of a first core sheet can flow to the transfer sheet and thereby be redistributed to any other core sheet. The transfer sheet can be variously oriented to the edges of the core sheets. The core sheets, spacer sheets and transfer sheet are preferably secured together, for example with bands or straps. The secured assembly can be overwrapped with geotextile fabric to form a system or indrain.
Another aspect of the present invention is a system comprising a plurality of alternating wide and narrow core sets. Each core set is comprised of parallel, alternating core sheets and spacer sheets. Fabric is disposed between some or all of the core sheets and spacer sheets. The alternating wide and narrow core sets provide multiple outwardly extending arms. The outermost ends of the arms are overwrapped with geotextile fabric. The outwardly extending arms function to provide a geometrical surface area advantage by increasing the system sidewall/soil surface interface area for a given length of leachate system, thereby enhancing leachate drainage to the subsoil environment.
In yet another aspect of the invention the leachate system comprises a plurality of alternating wide and narrow core sets and a transfer sheet adjacent to at least some of the core sheets.